One Piece
Great plot. not really visible plot holes. not much romance which is good/better for a shounen manga. great character progress and plot twists. no character is spoiled.
Assassination Classroom
good plot. nice enough character progress. quite predictable plot twists, but maybe not. not much romance, but damn it. There shouldn't be any romance in this.
Nanatsu No Taizai
great plot. nice plot twists. OP characters. sometimes, too OP but okay enough. not much character progress for the lady MC but understandable. It just figures with this manga that the OP ones are the ones that are always unable to fight when they are truly needed.
Fairy Tail
great plot. nice character progress. too damn OP characters. nice plot twists.
Fairy Tail Zero
great explanation on how mavis formed fairytail but too lacking on the finer details. like with the war and how the Fairy spells were made, not to mention the Lumen Histoire. Then there's what happened to her co-founders besides getting married and "dying". Too many unanswered questions.
Owari no Seraph
good plot. not enough character progress but well, yeah. Somewhat like Shingeki no Kyojin in plot style (read: up, up, up, down, down, down, down, up, down, down, you get it). NOT ENOUGH UPDATES.
Boku no Hero Academia
great plot. too many references to other mangas. slow character progress. predictable plot twists.
Terra Formars
great plot. too gore. too many death flags. too scientific. too graphic on the roaches. TOO DAMN GOOD.
Gate - Jietai Kare No Chi Nite, Kaku Tatakeri